The experiments proposed examine the development of the receptors and primary central relays in the olfactory system. The olfactory system has many desirable characteristics for studies of the mechanisms of neural maturation. It is highly organized, with clear lamination and a well-studied wiring diagram, facilitating quantitative examinations and making subtle alterations relatively easy to discern. Furthermore, many interesting forms of early plasticity have been demonstrated, including substantial sensitivity to early manipulations of either the type or amount of odor stimuli available. For example, early unilateral odor deprivation has been repeatedly demonstrated to result in some of the largest experience-induced changes observed in the central nervous system. The principal investigator and colleagues have been involved in studying the cascade of changes induced by functionally depriving the olfactory system in order to understand how early brain function directs normal brain maturation. The proposed research continues the quantitative examination of the sequential developmental changes occurring in normal and functionally restricted animals. Specifically, the principal investigator proposes to examine: 1) Rapid changes that occur in the olfactory bulb when the amount of odorant stimulation is abruptly decreased. Examinations will focus on rapid regulation of genomic expression and protein synthesis to identify which cell populations respond to afferent manipulations. 2) The effects of brief intervals of sensory restriction on the growth of the bulb. Reversible naris occlusion will be used to test signaling pathways in the bulb and to examine the possibility of recovery of normal growth patterns.